Heat flowmeter and device for the construction thereof



March 26, 1963 T. s. TE VELDE 3,

HEAT FLOWMETER AND DEVICE FOR THE CONSTRUCTION THEREOF Filed Jan. 7. 1958 Fir-av INVENTOR. 7765 S/[BOLT 7E V6205 United tates re 3,082,508 Patented Mar. 26, 1963 3,082,508 HEAT FLOWMETER AND DEVICE FOR THE CONSTRUCTION THEREOF Ties Siebolt te Velde, Delft, Netherlands, assignor to Nederiandse Centrale Organisatie voor Toegepast- Natuurwetenschappelijk Onderzoek, The Hague, Netherlands, a corporation of Holland Filed Jan. 7, 1958, Ser. No. 707,534 Claims priority, application Netherlands Jan. 7, 1957 Claims. (Cl. 29155.5)

The invention relates to heat flowmeters, consisting of a large number of thermo-elements which have been connected in series. Generally, these thermo-elements are embedded in an insulating synthetic resin.

Applicant has, for instance, developed and marketed a fiowmeter, the elements of which consist of a helix of constantan Wire having a diameter of 0.15 mm., one half of the helix having been coated electrolytically with copper. Said helixes were made by winding the constantan wire on a round mandril having a diameter of 3 mm. followed by removal of the mandril. In order to prevent this unsupported helix, which consists of many hundreds of windings, from wrenching during electrolytic coppering and during the following mounting (on wrenching the junctions would no longer all lie on the upper or lower side of the helix respectively) this helix, having a pitch which is approximately double the wire thickness is glued to a strip of paper, subsequently coppered and mounted. This treatment is time-consuming and cumbersome; moreover not more than about approximately 80 of these elements can be placed per square cm. surface of the flowmeter and treatment of helixes with a core-diameter of less than 3 mm. was impracticable. The sensitivity of a meter made with such a helix is approximately 1 mv. at a heat flow of 200 kcaL/hour sq. in. through a sheet of 1 sq. cm.

The invention relates to a heat Eflowmeter which is constructed according to the same principle, but is characterized by thermo-elements wound as a helix of metal wire or band about half of each turn of said helix being coated with a surface layer of la thermo-electrically dissimilar material :and which helix has a cross section having at least one flat side. Preferably the cross section of the helix is rectangular, the long sides of the rectangle having about the double length of the short sides, and with the junctions between the thermo-electrically dissimilar materials lying on the short sides. This makes it possible on the one hand to provide a larger number of elements per sq. cm. surface in the heat flowmeter and as a result to reduce the heat resistance, while on the other hand the treatments in respect of coating and mounting, necessary for the construction of the elements, become much simpler, as with a non-round helix wrenching of said helix during the treatment can easily be prevented.

It was e.g. found to be possible to wind constant'an wire with a diameter of 0.08 mm. on a rectangular mandril of 1 x 2 mm., which regularly pushes windings away and thereafter to coat said helix continuously electrolytically with copper in such a way that the junctions will lie at the short sides of the rectangle. Approximately 600 windings of helix per sq. cm. surface could be placed in the heat ilowmeter; the sensitivity is then approximately 1 mv. a heat flow of only 50 kcaL/hour sq. m. with 'a sheet of 1 sq. cm. Moreover, owing to the many thermo-elements per sq. cm. a much shorter adjusting time is obtained.

This opens up the possibility of measuring very small heat flows rapidly and thus also small heat ilow variations, so that these elements can be applied for very sensitive calorimeters and radiation meters.

In principle it is quite Well possible to make the dimen- 2 sions even smaller and to use for example a mandril of 0.3 x 0.5 mm.

In the figures below FIG. 1 represents a view of an embodiment of a heat flow-meter according to the invention.

FIG. 2 is a cross section through this meter according to the line II'I I in FIG. 1.

FIG. 3 represents a single winding showing the crosssection of the helix forming the thermo-elements which have been connected in series, on an enlarged scale.

FIG. 4 is a section through this winding according to the line IV=IV on an even more enlarged scale.

FIG. 5 is a diagram of the apparatus with which these helixes are made.

In FIG. 1 and 'FIG. 2 reference numeral 1 represents a sheet of polyvinyl chloride with a thickness of approximately 2.2 mm. Herein the helix 2 of constantan wire lies embedded, coppered over half of the winding. The windings of the helix are rectangular and have been Wound on a mandril of 1 x 2 mm.; the pitch of the helix is approximately 0.15 mm. The sheet has :an effective surface of approx. 18 x 18 mm.; the length of the helix is approximately 25 cm. and in total there are thus approximately 1600 thermo-elements present herein. The helix is fixed to contact strips 3, 4 which project beyond the sheet.

In FIG. 3 it is shown that the part 5 of each winding is coppered; the copper surface is indicated in FIG. 4 by reference numeral 6; the constantan surface by 7. The thickness of the copper layer is not arbitrary; the best result is obtained if the ratio of the surfaces of copper layer and constantan core of the cross section is approximately 0.065. Since a helix is electrolytically coppered, the copper layer at the outside of the helix, where the electric field is stronger, is as a rule thicker than the inside of the helix as indicated in FIG. 4. This exercises no disturbing influence, since only the proportion of the surfaces is important.

It is not necessary of course to use constantan wire as a helix and to coat said helix with copper, for other metals may also be used.

The helix may be of any material which is thermoelectrically dissimilar to the material of the coating.

For the electrolytical coating of the said helix can be used metals as e.g. platinum, gold, silver, iridium, palladium, rhenium, rhodium, chromium, iron, nickel, cobalt, copper, cadmium, zinc and tin.

The iollowing combinations of metals can be used to advantage platinum-platinum rhodium alloys, platinumplatin-um rhenium alloys, platinum-platinum iridium alloys, gold-palladium alloys, iridium-iridium rhodium alloys, nickel-nickel chromium alloys, nickel-copper, copper-nickel, copper-constantan, silver-constantan, iron-constantan, the last mentioned metal of the combination always representing the metal of the helix.

The helixes are made with the apparatus shown in FIG. 5 and can be embedded in a synthetic resin as e.g. polyvinyl chloride. This can be done by mounting the helix in a mould and pouring liquified polyvinylchloride (e.g. in the molten state or as a solution in the mould).

After solidification of the polyvinylchloride a flexible sheet containing the helix is obtained. Also other synthetic resins as for example unsaturated polyester resins and silicons can be used tor the same purpose.

After coppering the helix is preferably covered with an insulating lacquer layer in order to prevent the occurrence of a short circuit between adjacent windings owing to deformations, for example during the mounting of the helix.

The device for the construction of the helixes shown in FIG. 5 consists of a head 8. The constantan wire 13 of supplying coil 104's wound on the rectangular mandril 11 by the rotating arm 9, mounted on the driven disk 12. The rod is slowly lifted by a cam on the disk 14 connected with the disk 12 and then it is pressed down with a shock by the spring at the end of the cam, which movement is transferred to mandril 11 viathe body 16, rod 17 and lever 18, a Winding of the helix which has just been wound (which helix is taken to the left by the mandril) striking the springs 31 and as a result moves to the right with respect to the mandril. Thus the helix is pushed off the mandril. While it is still on the mandril the helix is annealed in the oven 19 in order to remove all the tensions in the material, so that after pushing off there is no longer anyinclination to wrenching. Subsequently the helix is led through the bath 21 with a defa-ttening liquid and subsequently over the rotating disk 22, which rotates in bath 23 through a lacquer. As a result a long side of the windings with the part of the short sides immediately connected thereto is covered with the thin layer of lacquer. This is dried in the oven 24 and the. helix is subsequently coppered electrolytically on the part which is not covered with lacquer in bath 25. After coppering rinsing is effected in bath 26, drying in drying oven 27 and subsequently the Whole helix is lacquered in bath '28. Finally the latter lacquer is baked in the oven 29 and the helix is wound on the driven coil 30.

I claim:

1. A process for the production of a helical series connection of thermo-elements of metal wire, the diameter of said Wire being less than 0.15 mm., comprising winding said wire as a helix on a mandril having at least one fiat side so as to provide for a straight part in each turn of said helix, annealing said helix on said mandril to remove any tensions therefrom, periodically pushing turns of said helix off said mandril, leading said helix over a lacquer-bathed disc so asto provide a part of each of said turns with a surface layer of insulating lacquer, and bath-coating the remaining uncovered part of each of said turns with a surface layer of a thermo-electrically dissimilar metal so that the junctions of the coated parts and the lacquered parts lie on either side of each of said straight parts of said turns. a I 2. The process of claim 2 including the steps of defattening the helical wire in a defattening liquid before providing the surface layer of lacquer and drying the lacquer layer before bath-coating the helix.

3. The process of claim 2 including the steps of rinsing and drying after bath-coating.

4. A process for the production of a helical series connection of thermo-elements of metal wire, the diameter of said wire being less than 0.15 mm., comprising winding said wire as a helix on a mandril, said mandril having a rectangular cross-section, annealing said helix on said mandril to remove any tensions therefrom, periodically pushing turns of said helix off said mandril, leading said helix over a lacquer-bathed disc so as to provide a part of each of said turns with a surface layer of insulating lacquer, and bath-coating the remaining uncovered part of each of said turns with a surface layer of a thermo-electrically dissimilar metal so that the junctions of the coated parts and the lacquered parts of each of the turns lie on the short sides of the rectangle.

5. A process for the production of a helical series connection of thermo-elements of metal wire, the diameter of said wire being less than 0.15 mm., comprising winding said wire as a helix on a mandril with at least one fiat side so as to provide for a straight part in each turn of said helix, annealing said helix on said mandril to remove any tensions therefrom, periodically pushing turns of said helix off said mandril, leading said helix through a defattening bath and then over a lacquer-bathed disc so as to provide a part of each of said turns with a surface layer of insulating lacquer, drying said lacquer layer, bathcoating the remaining uncovered part of each of said turns with a surface layer of a thermo-electrically dissimilar metal so that the junctions of the coated par-ts and the lacquered parts lie on either side of each of said straight parts of said turns, and then rinsing and drying said turns of said helix.

6. The process of claim 5 including the step of covering said rinsed and dried helix with an insulating lacquer layer and subsequently baking said layer.

7. A process for the production of a helical series connection o-f thermo-elements from metal wire, the diameter of said Wire being less than 0.15 mm, comprising Winding said Wire as a helix on a mandril, said mandril having a rectangular cross-section, the long side of which being approximately twice as long as the short side, an-

nealing said helix on said mandril toremove any tensions therefrom, periodically pushing turns of said helix off said mandril, leading said helix through a defattening bath and then over a lacquer-bathed disc so as to provide a part of each of said turns with a surface layer of insulating lacquer, drying said lacquer layer, bath-coating the remaining uncovered part of each of said turns with a surface layer of a thermo-electrically dissimilar metal so that the junctions of the coatedparts and the lacquered parts of each of the turns lie on the short sides of the rectangle, and then rinsing and drying said turns of said helix.

8. The process of claim 7, including the step of covering said rinsed and dried helix with an insulating lacquer layer and baking said layer.

9. A process for the production of a heat fiowmeter comprising winding a wire, the diameter of which is less than 0.15 mm., as a helix on a mandril having at least one flat side so as to provide for a straight part in each turn of said helix, annealing said helix on said mandril to remove any tensions therefrom, periodically pushing turns of said helix off said mandril, leading said helix through a defattening bath and then over a lacquer-bathed disc so as to provide a part of each of said turns with a insulating lacquer layer, baking said lacquer layer, and embedding said helix in a synthetic resin.

10. A process for the production of a heat fiowmeter comprising winding a wire, the diameter of which is less than 0.15 mm, as a helix on a mandril, said mandril having a rectangular cross-section, the long side of which being approximately twice as long as the short side, an-

nealing said helix on said mandril to remove any tensions therefrom, periodically pushing turns of said helix off said mandril, leading said helix through a dcfattening bath and then over a lacquer-bathed disc so as to provide a part of each of said turns with a surface layer of insulating lacquer, drying said lacquer layer, bath-coating the remaining uncovered part of each of said turns with a surface layer of a thermo-electrically dissimilar metal so that the junctions of the coated parts and the lacquered parts of each of the turns lie on the short sides of the rectangle rinsing and drying said turns of said helix, covering said rinsed and dried helix with an insulating lacquer layer, baking said lacquer layer, and embedding said helix in a synthetic resin. 7

' References Cited in the file of this patent UNITED STATES PATENTS 2,310,026 Higley Feb. 2, 1943 2,643,975 Neish June 30, 1953 2,680,710 Kenmore et -al June 8, 1954 2,699,424 Nieter Jan. 11, 1955 2,795,032 Kerstetter June '1 l, 1957 2,807,657 Jenkins et al Sept. 24, 1957 2,943,956 Robinson July 5, 1960 

1. A PROCESS FOR THE PRODUCTION OF A HELICAL SERIES CONNECTION OF THERMO-ELEMENTS OF METAL WIRE, THE DIAMETER OF SAID WIRE BEING LESS THAN 0.15 MM., COMPRISING WINDING SAID WIRE AS A HELIX ON A MANDRIL HAVING AT LEAST ONE FLAT SIDE SO AS TO PROVIDE FOR A STRAIGHT PART IN EACH TURN OF SAID HELIX, ANNEALING SAID HELIX ON SAID MANDRIL TO REMOVE ANY TENSIONS THEREFROM, PERIODICALLY PUSHING TURNS OF SAID HELIX OFF SAID MANDRIL, LEADING SAID HELIX OVER A LACQUER-BATHED DISC SO AS TO PROVIDE A PART OF EACH OF SAID TURNS WITH A SURFACE LAYER OF INSULATING LACQUER, AND BATH-COATING THE REMAINING UNCOVERED PART OF EACH OF SAID TURNS WITH A SURFACE LAYER OF A THERMO-ELECTRICALLY DISSIMILAR METAL SO THAT THE JUNCTIONS OF THE COATED PARTS AND THE LACQUERED PARTS LIE ON EITHER SIDE OF EACH OF SAID STRAIGHT PARTS OF SAID TURNS. 